This invention relates to a method of manufacturing electroluminescent lamps having surface designs and to lamps produced by this method.
As is well known in the art (e.g., see U.S. Pat. No. 5,346,718 issued on Sep. 13, 1994 and assigned to the present assignee), electroluminescent (EL) lamps are generally constructed as laminated or layered structures. FIG. 1 illustrates a side elevational view in cross section of an archetypal, prior art EL lamp 10. The drawing is not to scale, and the layers are greatly enlarged for purposes of illustration, it being understood that some of the layers referred to herein are quite thin. Furthermore, the bottom layer in the drawing is in actuality the face of the EL lamp 10 (the drawing shows the EL lamp 10 upside-down because this is how the different layers are deposited). The EL lamp 10 comprises a transparent substrate 11 having deposited thereon a first conductive layer 12. Note that the transparent substrate 11 serves as the face of the EL lamp 10. Commercially, the substrate 11 with the conductive layer 12 already on it is available in the form of Mylar.TM. (a registered trademark of E.I. duPont de Nemours & Co.) having an indium tin oxide (ITO) coating. On the first conductive layer 12, which may also be referred to as the front electrode, an electroluminescent layer 13 is deposited by silk screening or another suitable process. The electroluminescent layer 13, as known, comprises electroluminescent particles such as ZnS:Cu which are thoroughly mixed in a polymerizable resin, with the resin being subsequently polymerized. On the electroluminescent layer 13, an insulating layer 14 is deposited. The insulating layer 14 may be composed of barium titanate or other appropriate dielectrics, preferably having light reflective qualities. Finally, a second conductive layer 15, which may also be referred to as the back electrode, is deposited on the insulating layer 14. The second conductive layer 15 also preferably has light reflective qualities. The insulating layer 14 serves to maintain an electrical separation between the first and second conductive layers 12, 15.
Generally, the front electrode 12 is highly transparent to permit as much of the light emitted by an energized electroluminescent layer 13 to reach the face 11 of the EL lamp 10 as possible. As is known, the electroluminescent layer 13 is energized by application of an electrical potential between the front and back electrodes 12, 15. The problem with utilizing a highly transparent front electrode in an EL lamp is the dull, visually unappealing appearance whenever the electroluminescent layer is not energized. This is because no means are provided to adequately reflect the incident ambient light entering the face of the EL lamp. Without adequate reflection of the incident ambient light, the resin/electroluminescent particles mixture comprising the electroluminescent layer 13 appears dull and unappealing when not energized. Thus, it is one object of the present invention to provide an improved EL lamp which can adequately reflect incident ambient light, and the method of making the same.
It is another object of the present invention to provide an improved EL lamp which can adequately reflect incident ambient light and also transmit light emitted by the electroluminescent layer, and the method of making the same.
Another object of the present invention is to provide an improved EL lamp, the face of which has a predetermined configuration, and the method of making the same.
Yet another object of the present invention is to provide an improved EL lamp having lacquer of predetermined color applied to its face, and the method of making the same.
EL lamps have been modified to provide a lighted timepiece dial, as disclosed in U.S. Pat. No. 4,775,964 issued on Oct. 4, 1988 to Alessio et al. and assigned to the present assignee. Thus, still another object of the present invention is to provide an improved EL lamp, serving as an EL dial, having horological markings on its face, and the method of making the same.